This invention relates to a sterilization container for use in sterilizing, storing and transporting and presenting instruments, in particular medical instruments.
Most, reusable medical instruments require sterilization before each use. Many methods are employed for sterilization, but the most prevalent methods include: steam autoclaving, vapor phase chemical sterilization and vapor phase chemical sterilization in combination with a plasma field. The chemical sterilants include hydrogen peroxide and ethylene oxide. One of the most versatile, quickest and most effective methods employs an initial period of vapor phase hydrogen peroxide followed by application of an electromagnetic field which drives the hydrogen peroxide vapor into the plasma state of matter. The plasma phase enhances the sterilization and when the electromagnetic field is released the plasma free radicals recombine to form water and oxygen.
Typically, instruments are placed into a container and then the container is placed into the sterilization device. Portals for the passage of sterilizing media must be provided. Also, the container is usually provided with a filter material which allows passage of the sterilizing media through the portals and container yet prevents the ingress of microorganisms. The portal and filter material may be combined as in the Nichols U.S. Pat. No. 4,704,254, issued Nov. 3, 1987 and incorporated herein by reference, or the container may be provided with a plurality of apertures and then be wrapped prior to each sterilization in a filter wrapping material such as SPUNGUARD brand CSR wrap available from Kimberly Clark Corporation which is a spunbonded/meltblown/spunbonded (SMS) laminate consisting of nonwoven outer layers of spun-bonded polyolefins and an interior barrier layer of melt-blown polyolefins.
Usually, holding devices of one form or another hold one or more individual instruments within the container. The holding device may comprise clips or other such arrangements, which may or may not be specially adapted to hold a particular medical instrument. One popular holding device simply comprises a plurality of upwardly extending flexible projections, sometimes called fingers, which prevent the instruments from moving about within the container and provide minimal contact with the instruments. Typically, these are provided on a mat which lies in the bottom of the container.
The ideal sterilization container minimizes or eliminates areas in which liquids, particularly liquid water condensate from a steam autoclave, may collect, is compatible with all commonly employed sterilization procedures, has a long life, is easy to operate and can be provided for a reasonable cost. Containers presently known suffer from shortcomings which limit their performance in one or more of these areas. For instance, many trays designed for steam autoclaves are formed of stainless steel which may interfere with formation of a plasma in some systems. Other trays made of polymers may not have sufficient heat resistance to withstand repeated steam sterilization cycles. Some tray materials interact with chemical sterilants, and may even decompose the sterilant. Other materials may absorb excessive amounts of chemical sterilants, thereby decreasing the sterilization effectiveness by decreasing the amount of sterilant available for sterilizing.
When using mats with flexible fingers, condensate and other liquids may become trapped between the mat and the bottom of the tray, providing a potential breeding ground for microorganisms. Brooks, Jr., in U.S. Pat. No. 5,098,676, addresses this problem by providing a plurality of small feet on the bottom of the mat to elevate it off of the tray bottom. Allen et al., in U.S. Pat. No. 5,407,648, address the problem by providing ribs on the tray bottom upon which the mat rests. Both references teach a flat tray bottom which does not promote good drainage.
The present invention overcomes these and other limitations in the prior art and provides compatibility with hydrogen peroxide vapor, liquid or gas plasma, steam autoclaves, ethylene oxide and other chemical or heat based sterilizing methods. It is durable, inexpensive to produce, enhances drainage and limits condensate entrapment.
A sterilization container for sterilizing instruments according to the present invention comprises an enclosing wall, a base portion of the wall and a plurality of drainage apertures through the base portion. Drainage wells are associated with at least a portion of the drainage apertures. The drainage wells individually comprise a supporting surface above the exit aperture, and an exit surface between supporting surface and the exit aperture. The exit surface is oriented to direct liquid downwardly toward the exit aperture without entrapment. A flexible elastomeric mat is supported within the container upon the supporting surfaces, and has means for holding an instrument. The exit surfaces promote drainage of liquids from the container out through the drainage apertures associated therewith and the supporting surfaces support the flexible elastomeric mat.
Preferably, each drainage well is associated with a single drainage aperture, and the exit surfaces surround the drainage aperture associated therewith. If the supporting surface comprises a sharp edge, it to minimizes contact between the supporting surface and the mat while still providing adequate support for the mat. Preferably, the exit surface continuously slopes toward the drainage aperture associated therewith. The drainage wells may take the shape of inverted pyramids and be arranged in a uniform grid. The mat is suitably formed of silicone rubber and the means for holding an instrument can comprise a plurality of upwardly extending flexible projections. However, any known holding means may be substituted therefor. The mat preferably has a plurality of mat apertures, at least a portion of which preferably align with corresponding drainage apertures.
A method for sterilizing instruments according to the present invention is also provided. A flexible elastomeric mat is placed within a sterilization container, the container having an enclosing wall, a base portion of said wall, and a plurality of drainage apertures through the base portion. Drainage wells are associated with at least a portion of the drainage apertures, the drainage wells individually comprising a supporting surface above the exit aperture, and an exit surface between supporting surface and the exit aperture, the exit surface being oriented to direct liquid downwardly toward the exit aperture without entrapment. The mat is supported upon the supporting surfaces and the instrument is held in a position on the mat with a holding means. A sterilizing fluid is passed into the container and over the instrument and liquid is drained from within the container along the exit surfaces out through the drainage apertures associated therewith.